<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN"><!-- - Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC") - Copyright (C) 2001  Internet Software Consortium. - - Permission to use, copy, modify, and distribute this software for any - purpose with or without fee is hereby granted, provided that the above - copyright notice and this permission notice appear in all copies. - - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY - AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR - PERFORMANCE OF THIS SOFTWARE.--><!-- $Id: lwres_gnba.docbook,v 1.2 2004/09/20 18:00:50 mcr Exp $ --><refentry><refentryinfo><date>Jun 30, 2000</date></refentryinfo><refmeta><refentrytitle>lwres_gnba</refentrytitle><manvolnum>3</manvolnum><refmiscinfo>BIND9</refmiscinfo></refmeta><refnamediv><refname>lwres_gnbarequest_render</refname><refname>lwres_gnbaresponse_render</refname><refname>lwres_gnbarequest_parse</refname><refname>lwres_gnbaresponse_parse</refname><refname>lwres_gnbaresponse_free</refname><refname>lwres_gnbarequest_free</refname><refpurpose>lightweight resolver getnamebyaddress message handling</refpurpose></refnamediv><refsynopsisdiv><funcsynopsis><funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo><funcprototype><funcdef>lwres_result_t<function>lwres_gnbarequest_render</function></funcdef><paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef><paramdef>lwres_gnbarequest_t *<parameter>req</parameter></paramdef><paramdef>lwres_lwpacket_t *<parameter>pkt</parameter></paramdef><paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef></funcprototype><funcprototype><funcdef>lwres_result_t<function>lwres_gnbaresponse_render</function></funcdef><paramdef>lwres_context_t *ctx</paramdef><paramdef>lwres_gnbaresponse_t *req</paramdef><paramdef>lwres_lwpacket_t *pkt</paramdef><paramdef>lwres_buffer_t *b</paramdef></funcprototype><funcprototype><funcdef>lwres_result_t<function>lwres_gnbarequest_parse</function></funcdef><paramdef>lwres_context_t *ctx</paramdef><paramdef>lwres_buffer_t *b</paramdef><paramdef>lwres_lwpacket_t *pkt</paramdef><paramdef>lwres_gnbarequest_t **structp</paramdef></funcprototype><funcprototype><funcdef>lwres_result_t<function>lwres_gnbaresponse_parse</function></funcdef><paramdef>lwres_context_t *ctx</paramdef><paramdef>lwres_buffer_t *b</paramdef><paramdef>lwres_lwpacket_t *pkt</paramdef><paramdef>lwres_gnbaresponse_t **structp</paramdef></funcprototype><funcprototype><funcdef>void<function>lwres_gnbaresponse_free</function></funcdef><paramdef>lwres_context_t *ctx</paramdef><paramdef>lwres_gnbaresponse_t **structp</paramdef></funcprototype><funcprototype><funcdef>void<function>lwres_gnbarequest_free</function></funcdef><paramdef>lwres_context_t *ctx</paramdef><paramdef>lwres_gnbarequest_t **structp</paramdef></funcprototype></funcsynopsis></refsynopsisdiv><refsect1><title>DESCRIPTION</title><para>These are low-level routines for creating and parsinglightweight resolver address-to-name lookup request and response messages.</para><para>There are four main functions for the getnamebyaddr opcode.One render function converts a getnamebyaddr request structure &mdash;<type>lwres_gnbarequest_t</type> &mdash;to the lightweight resolver's canonical format.It is complemented by a parse function that converts a packet in thiscanonical format to a getnamebyaddr request structure.Another render function converts the getnamebyaddr response structure &mdash;<type>lwres_gnbaresponse_t</type>to the canonical format.This is complemented by a parse function which converts a packet incanonical format to a getnamebyaddr response structure.</para><para>These structures are defined in<filename>lwres/lwres.h</filename>.They are shown below.<programlisting>#define LWRES_OPCODE_GETNAMEBYADDR      0x00010002Utypedef struct {        lwres_uint32_t  flags;        lwres_addr_t    addr;} lwres_gnbarequest_t;typedef struct {        lwres_uint32_t  flags;        lwres_uint16_t  naliases;        char           *realname;        char          **aliases;        lwres_uint16_t  realnamelen;        lwres_uint16_t *aliaslen;        void           *base;        size_t          baselen;} lwres_gnbaresponse_t;</programlisting></para><para><function>lwres_gnbarequest_render()</function>uses resolver context<varname>ctx</varname>to convert getnamebyaddr request structure<varname>req</varname>to canonical format.The packet header structure<varname>pkt</varname>is initialised and transferred tobuffer<varname>b</varname>.The contents of<varname>*req</varname>are then appended to the buffer in canonical format.<function>lwres_gnbaresponse_render()</function>performs the same task, except it converts a getnamebyaddr response structure<type>lwres_gnbaresponse_t</type>to the lightweight resolver's canonical format.</para><para><function>lwres_gnbarequest_parse()</function>uses context<varname>ctx</varname>to convert the contents of packet<varname>pkt</varname>to a<type>lwres_gnbarequest_t</type>structure.Buffer<varname>b</varname>provides space to be used for storing this structure.When the function succeeds, the resulting<type>lwres_gnbarequest_t</type>is made available through<varname>*structp</varname>.<function>lwres_gnbaresponse_parse()</function>offers the same semantics as<function>lwres_gnbarequest_parse()</function>except it yields a<type>lwres_gnbaresponse_t</type>structure.</para><para><function>lwres_gnbaresponse_free()</function>and<function>lwres_gnbarequest_free()</function>release the memory in resolver context<varname>ctx</varname>that was allocated to the<type>lwres_gnbaresponse_t</type>or<type>lwres_gnbarequest_t</type>structures referenced via<varname>structp</varname>.Any memory associated with ancillary buffers and strings for thosestructures is also discarded.</para></refsect1><refsect1><title>RETURN VALUES</title><para>The getnamebyaddr opcode functions<function>lwres_gnbarequest_render()</function>,<function>lwres_gnbaresponse_render()</function><function>lwres_gnbarequest_parse()</function>and<function>lwres_gnbaresponse_parse()</function>all return<errorcode>LWRES_R_SUCCESS</errorcode>on success.They return<errorcode>LWRES_R_NOMEMORY</errorcode>if memory allocation fails.<errorcode>LWRES_R_UNEXPECTEDEND</errorcode>is returned if the available space in the buffer<varname>b</varname>is too small to accommodate the packet header or the<type>lwres_gnbarequest_t</type>and<type>lwres_gnbaresponse_t</type>structures.<function>lwres_gnbarequest_parse()</function>and<function>lwres_gnbaresponse_parse()</function>will return<errorcode>LWRES_R_UNEXPECTEDEND</errorcode>if the buffer is not empty after decoding the received packet.These functions will return<errorcode>LWRES_R_FAILURE</errorcode>if<structfield>pktflags</structfield>in the packet header structure<type>lwres_lwpacket_t</type>indicate that the packet is not a response to an earlier query.</para></refsect1><refsect1><title>SEE ALSO</title><para><citerefentry><refentrytitle>lwres_packet</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></refsect1></refentry>